Louis Klarevas of the University of Massachusetts at Boston contends that an assault-weapon ban would result in “drastic reductions in what I call gun massacres,” meaning incidents in which six or more people are killed. His data indicate that fatalities from these incidents fell during the years the previous assault-weapon ban was in effect:

The pattern here is real; it shows up in the data set compiled by Mother Jones — which puts the fatality cutoff at four, includes only incidents that occur in public, and excludes gang activity — as well. As you can see in a chart made by Alan Reynolds at Cato, while the ban years included a rash of school shootings including Columbine, they also included some unusually calm years in the early to mid 2000s. It’s worth noting, though, that if you look at all incidents including four or more fatalities, the pattern is no longer evident.

In addition, while recent shootings with incredibly high body counts have involved assault weapons, most mass shootings in general actually involve handguns. Indeed, in the Mother Jones data set, I can find fewer than 20 shootings that (A) involved assault weapons, (b) had six or more fatalities, and (c) were committed in the 30 years from 1984 to 2014. Splitting so few shootings into three periods and looking for a trend is a dubious exercise, though for what it’s worth there’s still a dip in fatalities.

My skepticism of banning assault weapons has always primarily relied on the questionable nature of the distinction. These are not fully automatic military weapons that spray bullets when you hold down the trigger (though “bump stocks” can now make them behave like that, and we should do something about that); they fire once per trigger pull, just like many hunting rifles, and in fact often use smaller-caliber ammunition. Capping magazine size might allow someone to tackle a shooter while he’s reloading, and would apply even if he’s using a handgun instead of a rifle, but it also restricts people’s ability to defend themselves against more typical acts of violence (police do not limit themselves to ten rounds), and extremely high-capacity magazines jam more often.

These data don’t eliminate that skepticism of mine, but they’re worth noting and considering.